1. Field of the Invention
The present invention relates to an illumination apparatus, an image sensor unit, an image reading apparatus, and an image forming apparatus. More particularly, the present invention relates to a scanner, a copying machine, and a compound machine as an image reading apparatus or an image forming apparatus and to an illumination apparatus and an image sensor unit used in the image reading apparatus, the image forming apparatus, and the like.
2. Description of the Related Art
A light-guide type illumination apparatus is known as an illumination apparatus used in an image sensor unit.
More specifically, light emitted by a light source provided on an end face in a longitudinal direction of a light guide formed in a rod shape is reflected and diffused in the light guide and propagated through the light guide, and the light is shaped into a line and emitted from an emission surface. In this way, the light is uniformly emitted in a main-scan direction of an original.
However, there is a problem that a dedicated light source according to the position and the shape of the light guide needs to be used to provide the light source on the end face in the longitudinal direction, and this increases the cost.
Therefore, for example, Japanese Laid-open Patent Publication No. 2009-117186 discloses an image sensor module including a light guide with a combination of a pyramid portion and a flat portion, the light guide including a light incident surface, an inclined surface, a light reflection surface, and a light emission surface. This allows using a general, inexpensive surface-mount light source.
The light guide can reflect light, which has entered from a direction different from the longitudinal direction of the light guide, in the longitudinal direction of the light guide based on the inclined surface and then emit the light from the light emission surface.
In the image sensor unit, illuminance of the light emitted from the light guide to the original needs to be uniform in the longitudinal direction of the light guide. However, the light may be leaked around the inclined surface when the light entered from the direction different from the longitudinal direction of the light guide is reflected in the longitudinal direction of the light guide based on the inclined surface as in the light guide of Japanese Laid-open Patent Publication No. 2009-117186.